Flight Delay Index FAQ

Frequently Asked Questions

What does the delay index tell me about my flights?

The delay index is a forecast of departure disruption at the airport. Specifically, it represents a score of the short-term, on-time, departure on-time performance at an airport adjusted for delay severity and cancellations.

Is a high number good or bad?

The delay index score ranges in value from 0 to 5. The higher the number, the more likely it is that your departure will be disrupted by delays or cancellations. For example, a 5 represents severely impacted departure conditions - many cancellations and delays. A score of 1 indicates few cancellations and departure delays.

How do you calculate the delay index?

We begin with the airport's departure on-time performance and take into account the severity of delay and cancellations. We use a time range covering the previous 1 hour and the next 2 hours. We then produce a 0 - 5 score where higher values indicate more severe departure disruptions.

How does your delay index differ from the information on the FAA airport delay map?

The FAA airport delay map shows the current status of air traffic control delays at US airports. It doesn't show any indications of cancellations or delays for reasons other than air traffic control directives. For example, on December 10, 2007, the FAA map showed "FAA on-time" for the Kansas City Airport (MCI) while we showed a delay index of 5 (as bad as it gets). In fact there were no air traffic control delays at MCI that day. However, nearly 15% of the flights at MCI were being cancelled due to really awful weather throughout the Midwest. This example shows the benefit of taking the approach of looking at the status of individual flights in aggregate to characterize airport conditions rather than the FAA's top down approach.

What are the little arrows that point left or right?

Those arrows show the direction of the delay index trend. A green arrow pointing left toward zero indicates that the delay index is decreasing (conditions are improving). A red arrow pointing right indicates that conditions are worsening.

How often is the delay index updated?

We update our delay index calculations approximately every 30 minutes to keep them fresh and relevant.

Can you alert me if a delay index increases?

We don't currently have an alert service specifically for airport delay index changes. However, you can use our alerts service to monitor your specific flight(s) and be notified by email or text message upon arrival, departure, cancellation or delay.

Where can I learn more about my specific flight?

For specific details on your flight, you should check using our flight status service. You could also schedule an email or text message alert

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